Heating system



Jan. 14, 1958' E. s. DAUGHERTY 2,819,886

' HEATING SYSTEM Filed Jan. 24, 1956 FIG. I.

FIG. 2.-

Fasfa INVENTOR.

S. DAU EHERTY HEATING SYSTEM Edgar Si Daugherty, Elkins Park, Pa.,assiguor to Cochrane Corporation, Philadelphia, Pa., a corporation ofPennsylvania Application January 24, 1956, Serial No. 561,044

4 Claims. (Cl. 261-19) This invention relates to heating systems of thedirect contact heating type and has particular reference to deaerators.

Depending upon the operation pressure of the deaerator, and the quantityof water stored in its storage compartment, there is an appreciableamount of potential heat available in the storage compartment which isliberated following a reduction in imposed steam pressure through thenormal supply source. The water stored in the storage compartment hasbeen heated to, or very close to, the temperature corresponding to thesaturation temperature of the steam pressure applied to the deaerator.If, for any reason, the applied steam pressure is reduced, from ashortage of steam from its input connection coincident with a continualdemand for steam in the deaerating compartment due to maintenance ofwater flow, the entire pressure within the deaerating compartment startsto deteriorate. The available heat in the stored water in the storagecompartment is then liberated in the form of flash vapor. The usualdowncomer is sealed below the water line in the storage compartment, andtherefore the major portion of the flash vapor which must travel fromthe storage compartment to the demand point in the deaeratingcompartment must travel through a passageway from the steam inlet regionof the deaerating compartment to the storage compartment above its waterline. For example, this type of phenomenon occurs quite frequently whena deaerator is operating on a turbine extraction point and the turbineload is reduced, reducing the extraction pressure.

Due to incidental resistances to flow in the system, pressuredifferentials are set up which, as will hereafter appear, may produceviolent surges of liquid into the deaerator not only flooding the sameleaving it inefiective for deaerating or heating but also causingphysical damage in the deaerating compartment due to the geyser action.

It is the general object of the present invention to provide properoperation in a deaerator or other direct contact heating device withavoidance of improper situations of the type just outlined. Detailedobjects of the invention relate to matters of operation and constructionand will become apparent from the following description, read inconjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic sectional view showing the invention appliedto a deaerator;

Figure 2 is a similar view showing an alternative form of the invention;and

Figure 3 is a third similar view showing still another modification ofthe invention.

For consistency of description, the invention will be described asapplied to a deaerator, but as will become apparent the invention isequally applicable to other direct contact heating devices in whichsimilar problems arise. The fluid involved will be referred to as waterbut it will he understood that the invention is applicable to the "icehandling of other fluids with or without involving the removal ofdissolved gases or vapors.

There will first be briefly indicated the conventional type of deviceand the shortcomings thereof which are obviated by the presentinvention. Figure 1 shows an apparatus provided in accordance with theinvention but quite similar in general form and operation to what hasbeen heretofore used. The apparatus pictured in Figure 1 comprises adeaerating compartment 2 which may be of any conventional type, forexample, tray type, spray type, atomizing type or reboiling type, andwhich is provided with a water inlet 4 and a steam inlet 6. The internaldetails of the deaerating compartment are immaterial to the matter ofthe present invention and it will be understood that there is provided,in the case of a deaerator, a suitable outlet for the air separated fromthe water. In

' the case of heaters in which separation of air or some gas or vapor isnot involved, the internal construction may be simply that suitable fordirect contact heating.

Associated with the deaerating compartment 2 is a storage compartmentwhere previously deaerated water is stored or wherein there may bestored heated water or other liquid if the apparatus is not a deaerator.The vapor space of the storage compartment 8 is connected to the steamsupply line 6 through the equalizing passageway 10. Water or otherheated liquid is delivered through the connection 12 from the storagecompartment, and in the case of a power system this passage woulddeliver the deaerated water to a conventional boiler feed pump.

Before proceeding further with the description, it may be pointed outthat the arrangement shown in Figure 1 is purely diagrammatic and notrepresentative of an actual physical arrangement and not intended to belimiting in its significance. While the deaerating compartment may besuperimposed on a storage compartment as illustrated with an externalequalizing passageway 10, it Will be understood that the particularphysical arrangement may be of any conventional type: for example, boththe deaerating compartment and the storage compartment may be containedin a single vertical cylindrical shell, a pair of separate verticalcylindrical shells, at single horizontal shell, a pair of separatehorizontal cylindrical shells, or any other combination involvingcylindrical, rectangular, spherical or otherwise shaped containers. Theequalizing passageway may be located internally of the structureinvolved or it may be provided by external piping.

A downcomer 14 is shown as providing delivery of the deaerated waterfrom the deaerating compartment 2 into the storage compartment 8. Ascommonly constructed at the present time the downcomer 14 extendsclosely adjacent to the mouth of the outlet 12, being spaced therefromso that there is substantial area of communication between the end ofthe downcomer and the end of the water outlet to the water within thestorage compartment 8 which is designed to receive excess water when thedemand for water is low and to supply water at a greater rate than thatat which it is supplied from the deaerating compartment when the demandis high. In the prior type of deaerator or heater one of the undesirablefeatures of operation is that, when there is a deterioration of pressurewithin the deaerator as described above, as the storage compartmenttends to flash, i. e., liberates steam bubbles, the water going from thedeaerator through outlet 12 to the boiler feed pump is not a mass ofliquid water only but a mixture of Water and steam bubbles with theresult that violent cavitation occurs and loss of suction and consequentpumping ability of the pump at a time when the boiler might be requiringconsiderable water. To minimize this result the downcomer pipe has, asjust described, been run from the deaerating compartment to the vicinityof the outlet connection 12 in the storage compartment so that the waterdelivered to the outlet connection is the coldest water in the unit, orthe water more closely corresponding to the saturation temperature atthe instantaneous pressure existing within the unit and consequentlyless apt to contain steam bubbles. While this tends to avoid the passageof steam bubbles to the boiler feed pump, there is an attendantdisadvantage to this construction in that, during a period of rapidpressure deterioration in the deaerating compartment, the volume ofwater contained in the downcomer also liberates steam at the same timeas that occurs in the water in the storage compartment. When a volume ofwater at the saturation temperature corresponding to the pressureimposed on the surface rapidly boils due to a reduction of the imposedpressure, the net result is a tremendous increase in volume andincreased elevation of the water level. The extent to which boiling andlevel increase occurs is dependent upon the ability of the storagecompartment to supply steam through passageway and connection 6, theability of the system to supply flash vapor up the downcomer pipe, therate of demand of steam in the deaerating compartment, and the potentialheat available. In particular, the supply of steam from the vapor spaceof the storage compartment to the deaerating compartment is controlledby the incidental resistances involved in this connection.

The effects of What has just been described is that large quantities ofwater may pass upwardly through the downcomer into the deaeratingcompartment flooding it and rendering it ineffective for deaeration andat the same time physical damage in the deaerating compartment mayresult due to the flow of a large amount of water at high velocityproducing impact therein. It may further be noted that in most designsof deaerators only the steam entering the deaerating compartment throughits normal steam connection 6 is elfective for deaeration. Vapor whichmay enter the deaerating compartment by reverse flow through thedowncomer may bypass the deaerating elements or may not flow through thedeaerating elements in normal fashion and is consequently not fullyeffective for deaeration.

Referring now to the novel matters involved in the arrangement shown inFigure 1, this arrangement is such as to provide the advantages of theprior system heretofore described but with avoidance of thedisadvantages thereof. As shown in Figure 1, the downcomer 14 terminatesat a point a relatively short distance below the deaerating compartment,the termination being desirably within the vapor space of the storagecompartment 8. As shown, the downcomer 14- opens below the upper edge ofa container 16 of relatively small volume as compared with that of thestorage compartment 8, and this container 16 is located so that overflowof water therefrom is received in an enlargement 18 of the upper end ofa downcomer 20 which terminates at 22 adjacent to the mouth of theoutlet 12 in the same fashion as in prior arrangements there terminatedthe lower open end of the downcomer corresponding to 14. In other words,in the prior arrangements the single downcomer running from thedeaerating compartment 2 to a point adjacent to the outlet 12 consistedof a single pipe essentially combining the downcomers 14 and 20 shown inFigure l but providing a continuous closed wall.

In the operation of What is shown in Figure 1, heating of the watersupplied at 4 takes place within the deaerator 2 by the action of steamentering at 6 in the usual fashion with condensation of the steam. Thedeaerated water flows downwardly through downcomer 14 into the container16 from which it overflows passing downwardly through the downcomer 20to its end 22. By reason of the fact that this end 22 is closelyadjacent to the mouth of the outlet 12, during normal operation thewater flowing to the boiler feed pump has its major proportion providedby the freshly deaerated water, with only a minor proportion taken fromthe storage compartment which serves in the usual fashion to receiveextra water through the opening adjacent to the lower end 22 of thedowncomer during periods of low demand by the boiler feed pump and feedsadditional water during periods of high demand. In view of the fact thatthe freshly deaerated water is cooler than that in the storagecompartment, if and when flashing occurs there is less likelihood thatthere will be a detrimental degree of separation of steam bubbles in thewater flowing to the boiler feed pump than would be the case if thewater supplying the pump was supplied from that which had remained for aconsiderable time in the storage compartment and had its temperatureraised therein substantially to the saturation temperature correspondingto the pressure conditions normally existing. Thus the arrangement shownin Figure 1 provides the same advantages as the arrangement which hasbeen used and has been above described. On the other hand, it will benoted that there is no direct connection between the substantialquantity of water which may exist in the downcomer 20 and the deaeratingcompartment, the continuity being interrupted by the free communicationof the upper portion of.the downcomer 20 with the vapor space in thestorage compartment 8. Accordingly, in the event that flashingconditions exist involving a degradation of pressure in the deaeratingcompartment 2, while there will be a pressure diflerential existing inview of resistance to flow of steam from the vapor space of the storagecompartment into the deaerating compartment, the differential pressurewhich exists will cause to enter the deaerator only the relatively smallquantity of water contained in the short downcomer 14 and the smallcontainer 16. While flashing will occur in the downcomer 20, theattendant expansion of volume will only cause the fluid to rise into theend 18 of the downcomer or thereabove without the possibility that thesudden surge which may then result will force a tremendous amount ofwater at high velocity into contact with the elements within thedeaerating compartrnent.

Accordingly, it will be clear that the present invention guards againstboth flooding of the deaerating compartment and damage due to violentimpact of water flowing thereinto.

While the possibility of the flashing of water in the downcomer 14 andcontainer 16 has been referred to, it may be noted that the small volumeof water thus involved is well diluted with colder water directly fromthe deaerator compartment so that there is a minimum of flashing of thisquantity of water and little tendency of its volume to increase to suchan extent as to cause even minor impact.

Furthermore, there is less flashing likely to occur in the downcomer 20than will occur in the downcomer of the prior arrangement connected atits upper end directly to the deaerator. In the last mentioned casethere would be a substantial difference of pressure between the lowerand upper ends of the single downcomer. In the arrangement illustratedin Figure 1 the pressure in the downcomer 20 is that of the vapor spaceof the storage compartment 8 rather than that existing in the deaerator2.

Figure 2 shows a modification of the invention which diflers from thatshown in Figure 1 only in mechanical details in that the container 16 isreplaced by a container 24 from which overflow takes place inwardly intothe upper end 28 of the downcomer 26 which opens at its lower end 30closely adjacent to the mouth of the outlet 12. As shown in Figure 2 thedowncomer 26 is arranged so as to be out of alignment with the downcomer14 so that water flashing therein enters the vapor space of the storagecompartment 8 and cannot pass directly to the deaerating compartment 2.It will be evident that the operation is essentially the same as thatwhich has been described in connection with Figure 1.

Figure 3 shows a further modification in which'the downcomer 14previously described is replaced by aii enlarged tubular portion 30 ofthe upper end of the downcomer which terminates adjacent to the mouth ofthe outlet 12. Within the enlargement 36 there is located a bafilearrangement 34 in the form of a downwardly facing cylinder the upper endof which communicates through pipe 36 with the vapor space in thestorage compartment 8. It will be evident that in this arrangement thereis interposed between the lower end of the downcomer 32 and thedeaerating compartment 2 a region within the bafiie member 34 which isat the pressure of the vapor space of the storage compartment 8. Thisbafile arrangement is at the upper end of the downcomer 30, 32 with theresult that conditions exist substantially identical, from thestandpoint of operation, with those described in connection with themodifications shown in Figures 1 and 2. Not only are the pressures ofthe same type, but the baflle 34 prevents violent upward movement of anyliquid into the deaerating compartment. Liquid moving upwardly from thedowncomer 32 will pass largely through connection 36 into the vaporspace of the storage compartment.

While deaeration has been particularly referred to in the foregoingdescription of construction and operation, it will be evident that theremoval of air from water entering at 4- has no particular part in theoperation involved, and reference has been made primarily to a deaeratorbecause there is special utility in the invention to the extent that itespecially corrects operating conditions in a system designed tominimize flashing in the portion of liquid passing to a boiler feedpump, and under these conditions the device would be ordinarily adeaerator. It will be obvious that the invention is applicable to otherdirect contact heating devices where similar problems may occur.

What is claimed is:

l. A heating system comprising a heating compartment, means directingwater and steam into said heating compartment, a storage compartment forwater from said heating compartment, an outlet for water from saidstorage compartment, a conduit opening below the water level in saidstorage compartment for directing freshly heated water downwardly fromsaid heating compartment substantially directly to said outlet so thatnormal flow of water from said outlet contains a major proportion offreshly heated water and a minor proportion of stored water from saidstorage compartment, and means preventing Water in said conduit frompassing upwardly into said heating compartment upon the occurrence ofsubstantial drop of pressure in said heating compartment relative to thepressure in said storage compartment.

2. A heating system comprising a heating compartment, means directingwater and steam into said heating compartment, a storage compartment forwater from said heating compartment, an outlet for water from saidstorage compartment, a conduit opening below the water level in saidstorage compartment for directing freshly heated water downwardly fromsaid heating compartment substantially directly to said outlet so thatnormal flow of water from said outlet contains a major portion offreshly heated water and a minor proportion of stored water from saidstorage compartment, and means providing free communication between theupper end of said conduit and vapor space in said storage compartment.

3. A system according to claim 1 provided with a container receivingwater from said heating compartment and providing overflow feeding saidconduit.

4. A system according to claim 2 provided with a container receivingwater from said heating compartment and providing overflow feeding saidconduit.

References Cited in the file of this patent UNITED STATES PATENTS

